firebird_1995

iTrader: (1)

Anyone else had issues with srp pistons?


I picked up a 383 golen engine from a guy (great guy btw) and he had a lot of blowby and low compression on #1 and #4. Faces of the pistons looked fine, but after removal was another story...

With the rings removed...


#4 piston. I didn't remove the rings but I'm sure the damage is similar. ..

He had this issue one before with the #8 cylinder and replaced it. Now, there was an issue with the tune. He was unfortunately at the mercy of a 73 year old tuner that refused to run anything other than a 1 bar map and maf sensor. His afr was right around 13.5 at 5600 rpm and 11# of boost on pump gas. Prior to the damage he was running on a pcm for less tune on low boost. When the "tuner" got a hold of it and he changed pulleys is when problems started...
I checked the ring gap and both rings are at .022" on the #1 piston. On the #4 piston, gap was .025" top ring and .022" second ring. I looked up JE's ring installation manual and they call for .0050 per inch of bore on the top ring which shakes out to .020 and .0055 on the second ring (.022). This is the chart for their recommended rings (assuming that's what golen installed) for "street moderate turbo/nitrous".

Keep in mind this engine has 25k on it and while I wouldn't expect there to be a LOT of wear to the rings, the current gap leads me to believe they may have been installed even tighter.
I wouldn't consider this a "blown race only" application but that would put the ring gaps at .024/.026 which is more along the lines of what the last set of rings I installed (Mahle I believe) called for.


Here are some comparison pictures on the three failures and their location....
#8 (previous failure)

#1

#4


The location of the damage is in the exact same spot on all three pistons.
On the quench pad area of the piston favoring the intake side of the chamber.
Block is zero decked, and was running a felpro 1074 head gasket (.039 thickness)


Heres an up close of the #4 showing the 3rd ring land getting ready to dislodge



It was running lean for sure and that very well could have been the only issue, but here's my problem..
It obviously needs a new pair of pistons at the least. I happen to have a set of the exact same (would have get them checked for weight and possibly weight matched to avoid rebalancing) of the pistons golen used, sitting on my shelf. In the research I've done I see that these 4032 srp pistons are pretty well limited to 100 hp per cylinder (at the crank). On his last dyno run he was at 605 hp to the tires through an m6 with the 60# injectors maxed out around 5600 and 11# of boost. (Its got a d1sc with pullies capable of 16#) It's a safe assumption to say the engine is capable of cresting 100 hp per cylinder so, do I
A) replace the pistons with what was in it
Or
B) upgrade to a 2618 alloy piston and get the bottom end rebalanced.

I intend to run e85 this time around with a set of 80# Siemens injectors (base pressure bumped up if necessary).

Engine is a golen 383 lt1 with trick flow heads, d1sc procharger on pump gas



Thoughts?

hrcslam

E85 should help. But...

Option #2.
Go with stronger pistons and re-balance.

firebird_1995

iTrader: (1)

That's what I'm leaning towards. Looking into some 2618 pistons now. Looks like wiesco may have one for my application. I've got a 3.75 stroke and 5.7 rods. Diamond only offers a 383 piston in a 6" stroke. Looking into probe now. Any other suggestions?

bufmatmuslepants

iTrader: (3)

Was that 73 year old tuner Ed Wright? He knows more about LTxs than almost anyone. Sounds more like the PO gave Ed less info or inaccurate info when he got it tuned. I would NOT start bashing Ed if he was the tuner.

firebird_1995

iTrader: (1)

Unless ed moved to south florida I highly doubt it. Refused to tune it speed density or with anything other than a 1 bar sensor, insisted that 60# injectors were sufficient, as soon as the maf maxed out at 480.80 grams around 4100 rpms injector duty cycle is at 80% and the fuel starts dropping off around 56-5800 when the injector duty cycle was 99.6%. I've never talked to ed but from what I've read that doesn't sound like something he would do. The owner was meticulous with his records and gave me a stack of receipts with the engine, so I don't think there was a lack of info given.

Purple Poncho

iTrader: (1)

13.5-1 AFR, 11psi and pump gas will do that to SRP pistons.

Look at these as an option:
http://www.cnc-motorsports.com/pisto...-chevy_sb.html

Get some bigger injectors as well.

firebird_1995

iTrader: (1)

I called srp and they said the 4032 alloy is only good to 10#. The je extreme duty 2618 is only good to 20#. That's what the guy said anyway...

nitrous2fast

iTrader: (2)

Well crap I guess my supercharged truck running 16psi is about to have 8 split pistons. lol

Boost pressure is a measure of restriction not of HP. lol There are plenty of 4032 alloy pistons holding a bunch more power than what your car is producing.

I also second that 13.5-1 AFR, 11psi and pump gas will do that to SRP pistons. It looks like you should find a new tuner fast.

moehorsepower

iTrader: (3)

Hell 13.5 A/F, 11 PSI, what was the timing? Any piston is going to give with that set up. 1 bar can be tuned if you know what your doing, but why? I always tune with 2 bar on forced inducted motors. No need for speed density, again if you know what your doing. Before anything, Get a real tune or go buy a couple of cases of pistons..

firebird_1995

iTrader: (1)

again, I bought the engine in this condition. I have no idea what the tune was, all I have is some data master logs to look at to get a glimpse of what was going on and some cracked pistons. I realize the tune was messed up.